Reverb Feedback Issues SOLVED

[makinrose]

Hi makinrose

We are assuming that with the reverb control at zero there is no howl? How about with the preamp volume down? Circuit-wise, this is like a DR reverb channel only, no normal channel. Hopefully each cathode has its own Rk and Ck as that is one step to true improvement of grounding.

It is nonintuitive, but you might try a rubber band on the recovery tube.Leave it in place until you resolve the problem.

You might also want to go backwards through your ground improvements to see if they really are.

Thanks for the reply. Correct---it's basically a Deluxe Reverb with just the Reverb/Vibrato Channel.  Correct a zero there no howl.  The feedback problem happens regardless of the pre-amp volume---in fact I can remove that tube and still get it.  The problem appears to be in the recovery stage for the verb since I can remove the 12AT7 and still generate feedback.  

The filtering is a compromise since there was not enough room for a filter cap for each triode. Instead I've got a filter cap for every two triodes in the pre-amp, a cap for the reverb. a cap for the tremolo, a cap for the driver and caps for the Va and Vs. It's not a perfect setup but I was hoping it would be better than stock. Going backward through is a good idea.